1. Field of the Invention
The present invention relates to a solid agent for separating carbon monoxide from a mixed gas containing carbon monoxide together with nitrogen, methane, carbon dioxide, hydrogen, etc. and also to a method for producing the agent.
2. Prior Art
Carbon monoxide is a basic raw material in synthetic chemistry and it is produced from coke and coal in water gas furnace, Winkler furnace, Lurgi furnace, Kopper's furnace, etc. It is also produced from natural gas and petroleum hydrocarbons using a steam reformation process and a partial oxidation process. In the foregoing process, the products are obtained in the form of a mixed gas containing carbon monoxide, hydrogen, carbon dioxide, methane, nitrogen, etc. The mixed gas thus obtained also contains a small amount of water. For example, the mixed gas has a composition of 35 to 40 percent carbon monoxide, 45 to 51 percent hydrogen, 4 to 5 percent carbon dioxide, 0.5 to 1.0 percent methane, 4 to 9 percent nitrogen and 1,000 to 20,000 ppm water. Likewise, carbon monoxide which is formed as a byproduct in iron mills, oil refineries or petrochemical plants is also in the form of a mixed gas.
For the use of such carbon monoxide as a raw material in synthetic chemistry, it is necessary to separate the carbon monoxide from the mixed gas.
Hydrogen is also an important raw material in the chemical industry and it is separated from various types of mixed gas or from waste gases of petrochemical plants, such as the waste gases from the process for dehydrogenation of the hydrocarbons. These waste gases frequently contain a small amount of carbon monoxide. Since the carbon monoxide is a poison to catalysts for reactions wherein hydrogen is used, it must be separated and removed. Also, these waste gases usually contain a small amount of water.
One method to separate and remove carbon monoxide from mixed gases is by means of a liquid which is a copper solution. This process involves the following steps. First, by applying a pressure of 150 to 200 atm to the mixed gas at room temperature, the carbon monoxide is separated and removed by letting it be adsorbed into the ammoniacal aqueous solution of cuprous formate or into a hydrochloric acid suspension of cuprous chloride. Then, by heating the copper solution under reduced pressure, the carbon monoxide is discharged and separated and the copper solution is regenerated. However, this cleaning process has certain shortcomings including a difficulty in controlling the operation for the prevention of the formation of precipitates, corrosion of the equipment, loss of solution and high contstruction costs due to the use of a high pressure.
On the other hand, a toluene solution of aluminium copper chloride (AlCuCl4) has an advantage that it is not affected by hydrogen, carbon dioxide, methane and nitrogen which are contained in the mixed gas and therefore, requires a low pressure to adsorb the carbon monoxide. Nevertheless, it is defective in that it reacts irreversibly with water thereby causing deterioration in the adsorbing power of the solution as well as creating precipitates with hydrochloric acid. Consequently, it is necessary to provide a strong dehydration process prior to the adsorption process in order to reduce the water content in the mixed gas to less than 1 ppm. Strict control of the amount of water is indispensable to this procedure. Furthermore, the use of this adsorbing solution has another disadvantage. That is, the mixing of the vapor of toluene used as the solvent into the collected carbon monoxide is unavoidable, making it necessary to further provide equipment for the removal of the toluene. Also, because of the use of a liquid form of adsorbent, restrictions are placed on the processing procedure.
Now, few solid form of adsorbents for carbon monoxide have been known. According to U.S. Pat. No. 4,019,879, copper (I) zeolite that is obtained by a reduction process conducted at a high temperature after having copper (II) ions adsorbed by the zeolite is capable of adsorbing the carbon monoxide. This adsorbent, however, has drawbacks in that the temperature required for its preparation is as high as 300.degree. to 350.degree. C. and that the dependence of the amount of carbon monoxide adsorbed upon the pressure and temperature is relatively small.
In addition to the above, various methods have been proposed, but none of them have proved satisfactory as the process for separating carbon monoxide from mixed gas.